Method for stabilizing amphiphilic block copolymer micelle composition containing poorly water-soluble drug

ABSTRACT

A method for stabilizing a poorly water-soluble drug-containing amphiphilic block copolymer micelle composition via simplified steps in short time is described. Also described is a stabilized poorly water-soluble drug-containing amphiphilic block copolymer micelle composition having improved stability.

This application is a Continuation-in-Part of U.S. patent applicationSer. No. 12/810,473, filed 24 Jun. 2010, which is a National StageApplication of International Patent Application No. PCT/KR2008/006021,filed Oct. 13, 2008, which claims the benefit of priority to KoreanPatent Application No. 10-2008-0098521, filed Oct. 8, 2008 and KoreanPatent Application No. 10-2007-0141181, filed Dec. 31, 2007, thedisclosures of all of which are hereby incorporated by reference intheir entireties. The International Application was published in Englishon 9 Jul. 2009 as WO 2009/084801. To the extent appropriate, a claim ofpriority is made to each of the above disclosed applications.

TECHNICAL FIELD

Example embodiments of the present invention relate to a method forstabilizing an amphiphilic block copolymer micelle compositioncontaining poorly water-soluble drug.

BACKGROUND

Submicronic particulate drug delivery systems using biodegradablepolymers have been studied for the purpose of carrying out intravenousadministration of drugs. Recently, it has been reported thatnanoparticle systems and polymeric micelle systems using biodegradablepolymers are useful technological systems that can modify the in vivodistribution of a drug to reduce undesired side effects and can provideimproved efficiency. Additionally, because such systems enable targeteddrug delivery, they can achieve controlled drug release to targetorgans, tissues or cells. In fact, such systems are known to haveexcellent compatibility with body fluids and to improve thesolubilization ability of a hardly soluble drug and the bioavailabilityof a drug.

Recently, there has been reported a method for preparing block copolymermicelles by chemically bonding a drug to a block copolymer comprising ahydrophilic segment and a hydrophobic segment. The block copolymer is anA-B type diblock copolymer polymerized from a hydrophilic segment (A)and a hydrophobic segment (B). In the above-mentioned block copolymer,polyethylene oxide is used as the hydrophilic segment (A) and apolyaminoacid or hydrophobic group-bonded polyaminoacid is used as thehydrophobic segment (B). Such drugs as Adriamycin or indomethacin can bephysically encapsulated within the cores of the polymeric micellesformed from the block copolymer, so that the block copolymer micellescan be used as drug delivery systems. However, the polymeric micellesformed from the block copolymer cause many problems in the case of invivo applications, since they cannot be hydrolyzed in vivo but aredegraded only by enzymes, have poor biocompatibility, and cause immuneresponses, or the like.

Therefore, many attempts have been made to develop core-shell type drugdelivery systems having improved biodegradability and biocompatibility.

For example, diblock or multiblock copolymers comprising polyalkyleneglycol as a hydrophilic polymer and polylactic acid as a hydrophobicpolymer are known to those skilled in the art. More particularly,acrylic acid derivatives are bonded to the end groups of such diblock ormultiblock copolymers to form copolymers. The resultant copolymers aresubjected to crosslinking to stabilize the polymeric micelles. However,methods for preparing such diblock or multiblock copolymers havedifficulties in introducing crosslinkers to the hydrophobic segments ofA-B or A-B-A type diblock or triblock copolymers for the polymers toform stable structures via crosslinking. Additionally, the crosslinkersused in the above methods may not ensure safety in the human bodybecause the crosslinkers have not been applied in the human body as yet.Furthermore, the crosslinked polymers cannot be degraded in vivo, andthus cannot be applied for in vivo use.

As another example, a so-called solvent evaporation process has beenknown as a method for preparing a polymer micelle composition. Thesolvent evaporation process can be applied as a large-scale process bywhich poorly water-soluble drugs, which are hardly soluble in water, canbe encapsulated within amphiphilic block copolymer micelles. However,utilization of the solvent evaporation process is limited with respectto the selection of a solvent, because the solvent should be an organicsolvent in which both poorly water-soluble drug and the polymer can bedissolved, and should have such a low boiling point that it can bevolatilized via evaporation. In addition, the organic solvent should bea pharmaceutically acceptable solvent, whose residue does not adverselyaffect the human body. Further, the solvent evaporation processessentially includes a step of exposing reagents to high temperature fora long period of time, and thus it may cause such problems asdegradation of pharmaceutically active ingredients or decreasedpharmacological effects.

SUMMARY OF THE INVENTION Technical Problem

Therefore, in an effort to solve the above-described problems associatedwith the related art, there is provided a method for stabilizing apoorly water-soluble drug-containing amphiphilic block copolymer micellecomposition via simplified steps in short time.

There is also provided a stabilized poorly water-soluble drug-containingamphiphilic block copolymer micelle composition having improvedstability.

Technical Solution

In an aspect, there is provided a method for stabilizing a poorlywater-soluble drug-containing amphiphilic block copolymer micellecomposition, comprising: (a) dissolving poorly water-soluble drug and anamphiphilic block copolymer into an organic solvent; and (b) adding anaqueous solution containing an ionizable salt thereto to form polymericmicelles.

In another aspect, there is provided a stabilized poorly water-solubledrug-containing amphiphilic block copolymer micelle compositioncomprising poorly water-soluble drug, an amphiphilic block copolymercontaining a hydrophilic block and a hydrophobic block, and an ionizablesalt.

Advantageous Effects

The stabilized poorly water-soluble drug-containing amphiphilic blockcopolymer micelle composition prepared by the method for stabilizationaccording to one embodiment disclosed herein has excellent stability sothat it can prevent rapid release of a drug.

BRIEF DESCRIPTION OF THE DRAWINGS

Description will now be given in detail with reference to certainexample embodiments of a stabilized poorly water-soluble drug-containingamphiphilic block copolymer micelle composition and a method forstabilizing the same illustrated in the accompanying drawings which aregiven hereinbelow by way of illustration only and thus are notlimitative, wherein:

FIG. 1 is the ¹H NMR spectrum of the diblock copolymer [mPEG-PLA]obtained from Preparation Example 1; and

FIG. 2 is the ¹H NMR spectrum of the diblock copolymer [mPEG-PLGA]obtained from Preparation Example 2.

MODE FOR INVENTION

Hereinafter, reference will now be made in detail to variousembodiments, examples of which are illustrated in the accompanyingdrawings and described below. While the invention will be described inconjunction with example embodiments, it will be understood that thepresent description is not intended to be limitative.

The method for stabilizing a poorly water-soluble drug-containingamphiphilic block copolymer micelle composition according to oneembodiment disclosed herein may comprise dissolving poorly water-solubledrug and an amphiphilic block copolymer into an organic solvent toprovide a polymer solution; and adding an aqueous solution containing anionizable salt to the polymer solution to form polymeric micelles,wherein the poorly water-soluble drug-containing amphiphilic blockcopolymer micelle composition comprises 0.1-30 wt % of poorlywater-soluble drug, 20-98 wt % of the amphiphilic block copolymercontaining a hydrophilic block (A) and a hydrophobic block (B), and0.1-50 wt % of the ionizable salt, based on the total dry weight of thecomposition. The poorly water-soluble drug-containing amphiphilic blockcopolymer micelle composition has excellent biodegradability andbiocompatibility, and provides a polymeric micelle structure havingrelatively improved stability.

The poorly water-soluble drug may be in an anhydrous or hydrated state,or amorphous or crystalline state. In one embodiment, the poorlywater-soluble drug may be present in the composition in an amount of0.1-30 wt %, specifically 0.5-15 wt %, and more specifically 1-7 wt %based on the total dry weight of the composition.

The term “poorly water-soluble drug” refers to any drug or bioactiveagent which has the water solubility of 33.3 mg/ml or less. Thisincludes anticancer agents, antibiotics, anti-inflammatory agents,anesthetics, hormones, antihypertensive agents, and agents for thetreatment of diabetes, antihyperlipidemic agents, antiviral agents,agents for the treatment of Parkinson's disease, antidementia agents,antiemetics, immunosuppressants, antiulcerative agents, laxatives,antifungals and antimalarial agents. Examples of poorly water-solubledrugs include taxane, ketoconazole, itraconazole, voriconazole,posaconazole, cyclosporine, cisapride, acetaminophen, aspirin, acetylsalicylic acid, indomethacin, naproxen, wafarin, papaverine,thiabendazole, miconazole, cinarizine, doxorubicin, omeprazole,cholecalciferol, melphalan, nifedipine, digoxin, benzoic acidtryptophan, tyrosine, phenyl alanine, azthreonam, ibuprofen,phenoxymethylpenicillin, thalidomide, methyl testosterone,prochlorperazine, hydrocortisone, dideoxypurine nucleoside, vitamin D2,sulfonamide, sulfonylurea, para-aminobenzoic acid, melatonin, benzylpenicillin, chlorambucil, diazepine, digitoxin, hydrocortisone butyrate,metronidazole benzoate, tobutamide, prostaglandin, fludrocortisone,griseofulvin, miconazole nitrate, leukotriene B4 inhibitor, propranolol,theophylline, flubiprofen, sodium benzoate, benzoic acid, riboflavin,benzodiazepine, phenobarbital, glyburide, sulfadiazine, sulfaethylthiadiazole, diclofenac sodium, phenyroin, hioridazine hydrochloride,bropyrimie, hydrochlorothiazide, fluconazole, rapamycin and derivativesor analogs thereof such as benzoyl rapamycin, everolimus, temsirolimus,pimecrolimus, biolimus, epothilone A, -B, -D, ixabepilone etc. andpharmaceutically acceptable salts thereof.

In one embodiment, the poorly water-soluble drug is a taxane. Examplesof taxane include paclitaxel, docetaxel, 7-epipaclitaxel, t-acetylpaclitaxel, 10-desacetyl-paclitaxel, 10-desacetyl-7-epipaclitaxel,7-xylosylpaclitaxel, 10-desacetyl-7-glutarylpaclitaxel,7-N,N-dimethylglycylpaclitaxel, 7-L-alanylpaclitaxel, cabazitaxel or amixture thereof. Particularly, paclitaxel or docetaxel may be used. Ataxane may be extracted from natural plants, or may be obtained bysemi-synthesis or plant cell cultivation.

In one embodiment, the amphiphilic block copolymer may comprise ahydrophilic block (A) and a hydrophobic block (B) linked with each otherin the form of A-B, A-B-A or B-A-B structure. Additionally, theamphiphilic block copolymer may form core-shell type polymeric micellesin its aqueous solution state, wherein the hydrophobic block forms thecore and the hydrophilic block forms the shell.

In one embodiment, the hydrophilic block (A) of the amphiphilic blockcopolymer may be polyethylene glycol (PEG) or monomethoxypolyethyleneglycol (mPEG). Particularly, it may be mPEG. The hydrophilic block (A)may have a weight average molecular weight of 500-20,000 daltons,specifically 1,000-5,000 daltons, and more specifically 1,000-2,500daltons.

The hydrophobic block (B) of the amphiphilic block copolymer may be awater-insoluble, biodegradable polymer. In one embodiment, thehydrophobic block (B) may be polylactic acid (PLA) orpoly(lactic-co-glycolic acid) (PLGA). In another embodiment, thehydrophobic block (B) may have a weight average molecular weight of500-20,000 daltons, specifically 1,000-5,000 daltons, and morespecifically 1,000-2,500 daltons. Hydroxyl end groups of the hydrophobicblock (B) may be protected with fatty acid groups, and particularexamples of the fatty acid groups include acetate, propionate, butyrate,stearate, palmitate groups, and the like. The amphiphilic blockcopolymer comprising the hydrophilic block (A) and the hydrophobic block(B) may be present in the composition in an amount of 20-98 wt %,specifically 65-98 wt %, and more specifically 80-98 wt % based on thetotal dry weight of the composition.

In another embodiment, the hydrophilic block (A) and the hydrophobicblock (B) may be present in the amphiphilic block copolymer in such aratio that the copolymer comprises 40-70 wt %, specifically 50-60 wt %of the hydrophilic block (A) based on the weight of the copolymer. Whenthe hydrophilic block (A) is present in a proportion less than 40%, thepolymer has undesirably low solubility to water, resulting in difficultyin forming micelles. On the other hand, when the hydrophilic block (A)is present in a proportion greater than 70%, the polymer becomes toohydrophilic to form stable polymeric micelles, and thus the compositionmay not be used as a composition for solubilizing poorly water-solubledrug.

The ionizable salt functions to improve the stability of the poorlywater-soluble drug-containing amphiphilic block copolymer micellecomposition. Particularly, the ionizable salt significantly improves thestability of the composition in its aqueous solution state. One possiblemechanism of the function of the ionizable salt is as follows.

The degree of encapsulation of a drug within a polymeric micellestructure is in proportion to the fraction of cores formed from thehydrophobic block of the polymer in an aqueous solution. Additionally,the stability of the polymeric micelles depends on the dynamicequilibrium state formed by the polymeric micelles in an aqueoussolution, i.e., on the equilibrium constant between the polymericmicelle state and the unimer state dissolved in water.

Although a large amount of poorly soluble drug can be encapsulatedwithin a polymeric micelle structure, the hydrophilic blocks of thepolymer micelles may be surrounded with a great amount of watermolecules upon the encapsulation of the drug, and thus the interactionbetween the water molecules and the hydrophilic blocks may weaken thehydrophobic interaction between hydrophobic blocks of the micelles,thereby destabilizing the micelles in a dynamic equilibrium state.Addition of the ionizable salt causes an electrostatic attraction forcebetween the ionizable salt and water, resulting in dissociation of watermolecules from the hydrophilic blocks of the polymeric micelles. As aresult, the hydrophobic interaction between the hydrophobic blocks,which otherwise would participate in loose interaction, increasesrelatively, so that stable micelle structures can be formed. Inaddition, the ionizable salt is not removed during the preparation ofthe composition according to one embodiment disclosed herein but remainsin the finished composition. Through the stabilization effect realizedby the ionizable salt, the poorly water-soluble drug-containingamphiphilic block copolymer micelle composition has excellent stability.

The ionizable salt is pharmaceutically acceptable one and may beselected from any ionizable salts as long as it does not cause hemolysisupon the contact with blood.

In one embodiment, the ionizable salt may be an electrolyte,specifically an inorganic salt. Preferably, the inorganic salt may be atleast one selected from the group consisting of sodium chloride, sodiumsulfate, magnesium chloride, phosphate salts (e.g. NaH₂PO₄, KH₂PO₄,Na₂HPO₄, K₂HPO₄), carbonate salts and bicarbonate salts (e.g. NaHCO₃,Na₂CO₃, KHCO₃, K₂CO₃). More particularly, the ionizable salt may besodium chloride.

In one embodiment, the ionizable salt may be an organic salt.Preferably, the organic salt may be at least one selected from the groupconsisting of lactate, citrate, malate, succinate, tartarate, fumarate,ascorbate, glutamate, gluconate, sebacinate, malonate, salicylate,acetate and sorbate salts of alkaline metal. More specifically, theorganic salt may be at least one selected from the group consisting ofsodium lactate, sodium citrate, sodium malate, sodium succinate, sodiumtartarate, sodium fumarate, sodium ascorbate, sodium glutamate, sodiumgluconate, sodium sebacinate, sodium malonate, sodium salicylate, sodiumacetate and potassium sorbate.

Especially, it may be sodium chloride. In another embodiment, theionizable salt may be present in the composition in an amount of 0.1-50wt %, specifically 0.5-20 wt %, and more specifically 1-10 wt %, basedon the total dry weight of the composition.

In another aspect, there is provided a method for stabilizing alyophilized composition comprising the poorly water-solubledrug-containing amphiphilic block copolymer micelle composition.

The lyophilized composition may further comprise a lyophilization aid.In one embodiment, the lyophilization aid may be at least one selectedfrom the group consisting of lactose, mannitol, sorbitol and sucrose.The lyophilization aid is added for the lyophilized composition tomaintain a cake form. In addition, the lyophilization aid serves to helpthe amphiphilic block copolymer micelle composition to formhomogeneously in short time during the reconstitution of the lyophilizedcomposition. In another embodiment, the lyophilization aid may be usedin an amount of 1-90 wt %, and more particularly 10-60 wt %, based onthe total dry weight of the lyophilized composition.

In one embodiment, the lyophilized composition may comprise 0.1-15 wt %of poorly water-soluble drug based on the total dry weight of thecomposition, upon the reconstitution in an aqueous solution.Additionally, upon the reconstitution, the amphiphilic block copolymermay be present at a concentration of 10-150 mg/mL, the ionizable saltmay be present at a concentration of 5-30 mg/mL (specifically, 10-20mg/mL), and the lyophilization aid may be present at a concentration of1-100 mg/mL. In another embodiment, the lyophilized composition can havea controlled micelle particle size in a range of 1-400 nm, and moreparticularly 5-200 nm in an aqueous solution, depending on the molecularweight of the copolymer.

In one embodiment, the poorly water-soluble drug-containing amphiphilicblock copolymer micelle composition may be formulated into the form ofan aqueous solution, powder or tablet. In another embodiment, thecomposition may be an injection formulation. For example, thecomposition may be reconstituted with distilled water for injection,0.9% physiological saline, 5% aqueous dextrose solution, and the like.When the composition is reconstituted, at least 95% of poorlywater-soluble drug is stable for 12 hours or more without precipitation.

In another embodiment, the method may further comprise, after step (b):

-   -   (c) adding a lyophilization aid to the polymeric micelles; and    -   (d) carrying out lyophilization.

When poorly water-soluble drug is encapsulated with a micellecomposition by using an organic solvent via a solvent evaporationprocess, rapid drug precipitation may occur in the poorly water-solubledrug-containing micelle composition after the composition isreconstituted in injection water and is left at room temperature. Thisis because the organic solvent used in the solvent evaporation processremains in the composition.

Therefore, according to one embodiment of the method disclosed herein,drug precipitation may be prevented by using an ionizable salt and aminimized amount of organic solvent. To minimize the amount of theorganic solvent still remaining in the finished composition, thecomposition needs to be dried at a high temperature of 60° C. or higherunder reduced pressure for at least 12 hours. However, suchreduced-pressure, high-temperature drying conditions may causedegradation of a drug. Thus, the method for stabilizing the poorlywater-soluble drug-containing amphiphilic block copolymer micellecomposition according to one embodiment disclosed herein uses aminimized amount of organic solvent so that the finished composition canbe directly subjected to lyophilization while avoiding a need for aseparate step of removing the organic solvent. The poorly water-solubledrug-containing amphiphilic block copolymer micelle compositioncontaining the ionizable salt and using a minimized amount of organicsolvent according to one embodiment disclosed herein can provide alyophilized composition which is free from precipitation of poorlywater-soluble drug for 12 hours or more when reconstituted into aninjection formulation.

In one embodiment, the organic solvent in step (a) may include at leastone selected from the group consisting of acetone, ethanol, methanol,ethyl acetate, acetonitrile, methylene chloride, chloroform, acetic acidand dioxane. The organic solvent may be used in an amount of 0.5-30 wt%, specifically 0.5-15 wt %, and more specifically 1-10 wt % based onthe weight of the resultant micelle composition. When the organicsolvent is used in an amount less than 0.5 wt %, there may be adifficulty in dissolving a drug. On the other hand, when the organicsolvent is used in an amount greater than 30 wt %, drug precipitationmay occur upon the reconstitution of the lyophilized composition.

In one example embodiment, the ionizable salt may be at least oneselected from the group consisting of sodium chloride, sodium sulfateand magnesium chloride. In addition, the ionizable salt may be used inan amount of 0.1-50 wt % based on the total dry weight of the micellecomposition. Step (b) may be performed at a temperature of 25° C. orlower.

In one embodiment, the method for stabilizing the poorly water-solubledrug-containing amphiphilic block copolymer micelle composition mayfurther comprise sterilizing the aqueous polymeric micelle solutionobtained from step (c) with a sterilization filter, before step (d) ofcarrying out lyophilization.

The poorly water-soluble drug-containing amphiphilic block copolymermicelle composition according to one embodiment disclosed herein may beorally or parenterally administered in the form of an aqueous solutionor powder. Parenteral administration includes administration viaintravascular, intramuscular, subcutaneous, intraperitoneal, nasal,rectal, ophthalmic, pulmonary or other routes. Oral administrationincludes administration in the form of tablets or capsules, or aqueoussolution itself.

In addition, the lyophilized composition according to one embodimentdisclosed herein causes little variation in the concentration ofdocetaxel in a reconstituted composition over time. However, when noionizable salt is added, docetaxel concentration decreases after thelapse of one hour.

The following examples are not intended to be limitative.

PREPARATION EXAMPLE 1 Synthesis of Monomethoxypolyethyleneglycol-Polylactide (mPEG-PLA) Block Copolymer (A-B Type)

First, 5.0 g of monomethoxypolyethylene glycol (number average molecularweight: 2,000 daltons) is introduced into a 100 mL two-neck round-bottomflask, and is heated to 130° C. under reduced pressure (1 mmHg) for 3-4hours to remove water therefrom. Next, the flask is purged with nitrogengas, and stannous octoate (Sn(Oct)₂) is added thereto as a reactioncatalyst using a syringe in an amount of 0.1 wt % (10.13 mg, 25 mmol)based on the weight of D- and L-lactides. After the reaction mixture isagitated for 30 minutes, it is subjected to depressurization (1 mmHg) at130° C. for 1 hour to remove the solvent (toluene) in which the catalystis dissolved. Then, 10.13 g of purified lactide is added thereto, andthe resultant mixture is heated at 130° C. for 18 hours. After heating,the resultant polymer is dissolved into methylene chloride, and is addedto diethyl ether to cause precipitation of the polymer. The resultantpolymer is dried in a vacuum oven for 48 hours.

The copolymer, monomethoxylpolyethylene glycol-polylactide (mPEG-PLA),has a number average molecular weight of 2,000-1,765 daltons. Analysisof the copolymer performed by ¹H-NMR reveals that the copolymer is anA-B type diblock copolymer (see FIG. 1).

PREPARATION EXAMPLE 2 Synthesis of Monomethoxypolyethyleneglycol-Poly(lactic-co-glycolic acid) (mPEG-PLGA) Block Copolymer (A-BType)

A block copolymer is obtained by reacting monomethoxypolyethylene glycol(number average molecular weight: 5,000 daltons), lactide and glycolidein the presence of stannous octoate as a catalyst at 120° C. for 12hours in the same manner as Preparation Example 1.

The copolymer, monomethoxypolyethylene glycol-poly(lactic-co-glycolicacid) (mPEG-PLGA), has a number average molecular weight of 5,000-4,000daltons and is an A-B type copolymer. Analysis of the copolymerperformed by ¹H-NMR reveals that the copolymer is an A-B type diblockcopolymer (see FIG. 2).

EXAMPLE 1 Preparation of Mpeg-PLA Block Copolymer Micelle CompositionContaining Sodium Chloride and Docetaxel

First, 760 mg of the amphiphilic block copolymer, mPEG-PLA (numberaverage molecular weight: 2,000-1,765 daltons), obtained fromPreparation Example 1 is completely dissolved into 0.2 mL of ethanol at60° C. to provide a clear ethanol solution comprising the copolymer. Theethanol solution is cooled to 25° C., and 20 mg of docetaxel is addedthereto and the resultant solution is agitated until docetaxel iscompletely dissolved.

Next, aqueous solutions each containing 0.9 wt % and 1.8 wt % of sodiumchloride are prepared in separate containers. Each aqueous solution isadded to the ethanol solution comprising the copolymer in an amount of 4mL, and the resultant mixture is agitated at 40° C. for 10 minutes toform an aqueous polymeric micelle solution.

Then, 100 mg of D-mannitol is dissolved into each solution, and theresultant solution is filtered through a filter with a pore size of 200nm to remove undissolved docetaxel, followed by lyophilization.

The lyophilized composition is subjected to liquid chromatography asfollows to determine the content of docetaxel. Additionally, particlesize is measured by a dynamic light scattering (DLS) method. The resultsare shown in the following Table 1.

TABLE 1 Docetaxel Particle Size (mg) (mg) Content (wt %) (nm) 760 20 3699.9 18 760 20 72 99.8 19

Liquid Chromatography

-   1) Column: a stainless steel column having a length of 250 mm and an    inner diameter of 4.6 mm and packed with pentafluorophenyl-coated    particles having a particle diameter of 5 μm and a pore diameter of    300 Å.-   2) Mobile Phase: acetonitrile:methanol:water=26:32:420-   3) Flow Rate: 1.5 mL/min-   4) Loading Amount: 20 μL-   5) Detector: UV absorption spectrometer (measurement wavelength: 232    nm)

EXAMPLE 2 Preparation of Mpeg-PLA Block Copolymer Micelle CompositionContaining Magnesium Chloride and Paclitaxel

First, 100 mg of the amphiphilic block copolymer, mPEG-PLA (numberaverage molecular weight: 2,000-1,765 daltons), obtained fromPreparation Example 1 is completely dissolved into 0.1 mL of ethanol at60° C. to provide a clear ethanol solution comprising the copolymer. Theethanol solution is cooled to 25° C., and 20 mg of paclitaxel is addedthereto and the resultant solution is agitated until paclitaxel iscompletely dissolved.

Next, aqueous solutions each containing 0.9 wt % and 1.8 wt %of—magnesium chloride are prepared in separate containers. Each aqueoussolution is added to the ethanol solution comprising the copolymer in anamount of 4 mL, and the resultant mixture is agitated at 40° C. for 10minutes to form an aqueous polymeric micelle solution.

Then, 39 mg of D-mannitol is dissolved into each solution, and theresultant solution is filtered through a filter with a pore size of 200nm to remove undissolved paclitaxel, followed by lyophilization.

The lyophilized composition is subjected to the liquid chromatography asdescribed in Example 1 to determine the content of paclitaxel.Additionally, particle size is measured by a DLS method. The results areshown in the following Table 2.

TABLE 2 mPEG-PLA Paclitaxel Paclitaxel Particle Size (mg) (mg) MgCl₂(mg) Content (wt %) (nm) 100 20 36 99.7 21 100 20 72 99.9 22

EXAMPLE 3 Preparation of Mpeg-PLGA Block Copolymer Micelle CompositionContaining Sodium Chloride and Docetaxel

First, 760 mg of the amphiphilic block copolymer, mPEG-PLGA (numberaverage molecular weight: 5,000-4,000 daltons), obtained fromPreparation Example 2 is completely dissolved into 0.2 mL of acetone at50° C. to provide a clear acetone solution comprising the copolymer. Theacetone solution is cooled to 25° C., and 40 mg of docetaxel is addedthereto and the resultant solution is agitated until docetaxel iscompletely dissolved.

Next, 8 mL of an aqueous solution containing 0.9 wt % of sodium chlorideis added to the acetone solution comprising the copolymer and furthercontaining the drug, and the resultant mixture is agitated at 25° C. for20 minutes to form a homogeneous solution. Once the homogeneous solutionis formed, 200 mg of D-mannitol is dissolved into the solution toprovide a clear aqueous polymeric micelle solution. Finally, the aqueouspolymeric micelle solution is filtered through a filter with a pore sizeof 200 nm to remove undissolved docetaxel, followed by lyophilization.

The lyophilized composition is subjected to the liquid chromatography asdescribed in Example 1 to determine the content of docetaxel.Additionally, particle size is measured by a DLS method.

Docetaxel content: 101. 3 wt %.

Particle size: 35 nm.

EXAMPLE 4 Preparation of Mpeg-PLGA Block Copolymer Micelle CompositionContaining Magnesium Chloride and Paclitaxel

First, 100 mg of the amphiphilic block copolymer, mPEG-PLGA (numberaverage molecular weight: 5,000-4,000 daltons), obtained fromPreparation Example 2 is completely dissolved into 0.2 mL of acetone at50° C. to provide a clear acetone solution comprising the copolymer. Theacetone solution is cooled to 25° C., and 40 mg of paclitaxel is addedthereto and the resultant solution is agitated until paclitaxel iscompletely dissolved.

Next, 8 mL of an aqueous solution containing 0.9 wt % of magnesiumchloride is added to the acetone solution comprising the copolymer andfurther containing the drug, and the resultant mixture is agitated at25° C. for 20 minutes to form a homogeneous solution. Once thehomogeneous solution is formed, 53 mg of D-mannitol is dissolved intothe solution to provide a clear aqueous polymeric micelle solution.Finally, the aqueous polymeric micelle solution is filtered through afilter with a pore size of 200 nm to remove undissolved paclitaxel,followed by lyophilization.

The lyophilized composition is subjected to high-performance liquidchromatography (HPLC) to determine the content of docetaxel.Additionally, particle size is measured by a DLS method.

Docetaxel content: 99.7 wt %.

Particle size: 37 nm.

COMPARATIVE EXAMPLE 1 Preparation of Mpeg-PLA Block Copolymer MicelleComposition Containing no Inorganic Salt

First, 760 mg of the amphiphilic block copolymer, mPEG-PLA (numberaverage molecular weight: 2,000-1,765 daltons), obtained fromPreparation Example 1 is completely dissolved into 0.2 mL of ethanol at60° C. to provide a clear ethanol solution comprising the copolymer. Theethanol solution is cooled to 25° C., and 20 mg of docetaxel is addedthereto and the resultant solution is agitated until docetaxel iscompletely dissolved.

Next, 4 mL of distilled water for injection is added to the ethanolsolution comprising the copolymer, and the resultant mixture is agitatedat 40° C. for 10 minutes to form a homogeneous solution. Once thehomogeneous solution is formed, 100 mg of D-mannitol is dissolved intothe solution to provide a clear aqueous polymeric micelle solution.Finally, the aqueous polymeric micelle solution is filtered through afilter with a pore size of 200 nm to remove undissolved docetaxel,followed by lyophilization.

The lyophilized composition is subjected to HPLC to determine thecontent of docetaxel. Additionally, particle size is measured by a DLSmethod.

Docetaxel content: 100.3 wt %.

Particle size: 18 nm.

EXPERIMENTAL EXAMPLE 1

Stability Test

The sodium chloride-containing polymeric micelle compositions accordingto Example 1 are compared with the polymeric micelle compositioncontaining no inorganic salt according to Comparative Example 1 in termsof the stability of the aqueous solution at 37° C.

Each of the lyophilized compositions according to Example 1 andComparative Example 1 is diluted with distilled water for injection to adocetaxel concentration of 1 mg/mL. While each diluted solution is leftat 37° C., concentration of docetaxel contained in each micellestructure is measured over time. The results are shown in the followingTable 3.

TABLE 3 Docetaxel mPEG- Initial Docetaxel Concentration PLA DocetaxelNaCl Concentration After 12 Hours (mg) (mg) (mg) (mg/mL) (mg/mL) Comp.760 20 0 1.0 0.41 Ex. 1 Ex. 1 760 20 36 1.0 0.95 760 20 72 1.0 0.99

As can be seen from the results of Table 3, the compositions accordingto Example 1 cause no precipitation of docetaxel even after the lapse of12 hours, while the composition according to Comparative Example 1 showsan amount of docetaxel precipitation of 59% after the lapse of 12 hours.It can be seen from the above results that addition of sodium chloridemay increase the docetaxel retainability of a micelle composition byabout at least two times. Additionally, it can be also seen that ahigher ratio of the amount of the inorganic salt to that of theamphiphilic block copolymer provides the micelle composition with higherstability.

EXAMPLES 5˜8 AND COMPARATIVE EXAMPLE 2 Preparation of mPEG-PLA BlockCopolymer Micelle Composition Containing Various Ionizable Salts andDocetaxel

First, 380 mg of the amphiphilic block copolymer, mPEG-PLA (numberaverage molecular weight: 2,000-1,765 daltons), obtained fromPreparation Example 1 is completely dissolved into 2.0 mL of ethanol at60° C. to provide a clear ethanol solution comprising the copolymer. Theethanol solution is cooled to 30° C., and 20 mg of docetaxel is addedthereto and the resultant solution is agitated until docetaxel iscompletely dissolved. The ethanol is completely evaporated from thesolution by using a rotary evaporator to form a polymer-drug matrix.

Next, aqueous solutions each containing ionizable salts are prepared inseparate containers. Each aqueous solution is added to the polymer-drugmatrix, and the resultant mixture is agitated at 30° C. for 10 minutesto form an aqueous polymeric micelle solution.

Then, 100 mg of D-mannitol is dissolved into each solution, and theresultant solution is filtered through a filter with a pore size of 200nm to remove undissolved docetaxel, followed by lyophilization.

The lyophilized composition is reconstituted with water for injection(WFI) and subjected to high pressure liquid chromatography to determinethe content of docetaxel. Additionally, particle size is measured by adynamic light scattering (DLS) method. The results are shown in thefollowing Table 4.

TABLE 4 Examples Exam- Exam- Exam- Comparative Components ple 5 ple 6ple 7 Example 8 Example 2 Docetaxel 20.0 20.0 20.0 20.0 20.0 (mg)mPEG-PLA 380.0 380.0 380.0 380.0 380.0 (mg) Sodium Citrate 58.8 — — — —(mg) Sodium — 12.4 — — — Carbonate(mg) Sodium — — 36.0 — — Phosphate,monobasic (mg) Sodium Acetate — — — 16.4 — (mg) D-Mannitol (mg) 100.0100.0 100.0 100.0 100.0 WFI 19.5 19.5 19.5 19.5 19.5 Particle Size 20.219.9 19.9 19.0 20.9 (nm) pH 7.6 9.9 4.5 6.6 4.4 Initial Docetaxel 1.01.0 1.0 1.0 1.0 Concentration (mg/mL) Docetaxel 0.92 0.96 0.94 0.95 0.57Concentration After 24 hr Incubation at 25° C. (mg/mL)

EXAMPLES 9˜12 AND COMPARATIVE EXAMPLE 3 Preparation of mPEG-PLA BlockCopolymer Micelle Composition Containing Various Ionizable Salts andPaclitaxel

First, 500 mg of the amphiphilic block copolymer, mPEG-PLA (numberaverage molecular weight: 2,000-1,765 daltons), obtained fromPreparation Example 1 is completely dissolved into 2.0 mL of ethanol at60° C. to provide a clear ethanol solution comprising the copolymer. Theethanol solution is cooled to 40° C., and 100 mg of paclitaxel is addedthereto and the resultant solution is agitated until paclitaxel iscompletely dissolved. The ethanol is completely evaporated from thesolution by using a rotary evaporator to form a polymer-drug matrix.

Next, aqueous solutions each containing ionizable salts are prepared inseparate containers. Each aqueous solution is added to the polymer-drugmatrix, and the resultant mixture is agitated at 40° C. for 10 minutesto form an aqueous polymeric micelle solution.

Then, 250 mg of anhydrous lactose is dissolved into each solution, andthe resultant solution is filtered through a filter with a pore size of200 nm to remove undissolved paclitaxel, followed by lyophilization.

The lyophilized composition is reconstituted with water for injection(WFI) and subjected to liquid chromatography to determine the content ofpaclitaxel. Additionally, particle size is measured by a dynamic lightscattering (DLS) method. The results are shown in the following Table 5.

TABLE 5 Examples Exam- Exam- Exam- Comparative Components Example 9 ple10 ple 11 ple 12 Example 3 Paclitaxel 100.0 100.0 100.0 100.0 100.0 (mg)mPEG-PLA 500.0 500.0 500.0 500.0 500.0 (mg) Sodium Citrate 58.8 — — — —(mg) Sodium — 12.4 — — — Carbonate(mg) Sodium — — 36.0 — — Phosphate,monobasic (mg) Sodium Acetate — — — 16.4 — (mg) Anhydrous 250.0 250.0250.0 250.0 250.0 lactose (mg) WFI 19.5 19.5 19.5 19.5 19.5 ParticleSize 21.2 19.8 19.7 19.4 19.7 (nm) pH 6.8 9.6 3.4 5.5 3.1 InitialPaclitaxel 5.0 5.0 5.0 5.0 5.0 Concentration (mg/mL) Paclitaxel 4.764.91 4.72 4.83 4.61 Concentration After 24 hr Incubation at 25° C.(mg/mL)

EXAMPLES 13˜14 AND COMPARATIVE EXAMPLE 4 Preparation of mPEG-PLA BlockCopolymer Micelle Composition Containing Various Ionizable Salts andTemsirolimus

First, 390 mg of the amphiphilic block copolymer, mPEG-PLA (numberaverage molecular weight: 2,000-1,765 daltons), obtained fromPreparation Example 1 is completely dissolved into 2.0 mL ofdichloromethane at 60° C. to provide a clear dichloromethane solutioncomprising the copolymer. The dichloromethane solution is cooled to 40°C., and 25 mg of temsirolimus is added thereto and the resultantsolution is agitated until temsirolimus is completely dissolved. Thedichloromethane is completely evaporated from the solution by using arotary evaporator to form a polymer-drug matrix.

Next, aqueous solutions each containing ionizable salts are prepared inseparate containers. Each aqueous solution is added to the polymer-drugmatrix, and the resultant mixture is agitated at 40° C. for 10 minutesto form an aqueous polymeric micelle solution.

Then, 275 mg of D-mannitol is dissolved into each solution, and theresultant solution is filtered through a filter with a pore size of 200nm to remove undissolved temsirolimus, followed by lyophilization.

The lyophilized composition is reconstituted with water for injection(WFI) and subjected to liquid chromatography to determine the content oftemsirolimus. Additionally, particle size is measured by a dynamic lightscattering (DLS) method. The results are shown in the following Table 6.

TABLE 6 Examples Comparative Components Example 13 Example 14 Example 4Temsirolimus (mg) 25.0 25.0 25.0 mPEG-PLA (mg) 287.5 287.5 287.5 SodiumChloride (mg) 90.0 — — Sodium Phosphate, — 36.0 — monobasic (mg)D-Mannitol (mg) 275.0 275.0 275.0 WFI (mL) 9.5 9.5 9.5 Particle Size(nm) 21.7 20.9 22.9 pH 3.2 3.4 3.1 Initial Temsirolimus 2.50 2.50 2.50Concentration (mg/mL) Temsirolimus Concentration 2.46 2.48 2.23 After 24hr Incubation at 25° C. (mg/mL)

Description has been given in detail with reference to exampleembodiments. However, it will be appreciated by those skilled in the artthat changes may be made in these embodiments without departing from theprinciples and spirit of the method for stabilizing the poorlywater-soluble drug-containing amphiphilic block copolymer micellecomposition, the scope of which is defined in the accompanying claimsand their equivalents.

We claim:
 1. A method for stabilizing a poorly water-solubledrug-containing amphiphilic block copolymer micelle composition,comprising the steps of: dissolving poorly water-soluble drug and anamphiphilic block copolymer into an organic solvent to provide a polymersolution; adding an aqueous solution containing an ionizable salt to thepolymer solution to form polymeric micelles; adding a lyophilization aidto the polymeric micelles; and carrying out lyophilization, wherein thesteps are carried out in sequence, and wherein the poorly water-solubledrug-containing amphiphilic block copolymer micelle composition consistsof 0.1-30 wt % of poorly water-soluble drug, 20-98 wt % of theamphiphilic block copolymer containing a hydrophilic block (A) and ahydrophobic block (B), 0.1-50 wt % of the ionizable salt, and 1-60 wt %of lyophilization aid, based on the total dry weight of the composition,and wherein the hydrophilic block (A) is polyethylene glycol ormonomethoxypolyethylene glycol, and the hydrophobic block (B) ispolylactic acid (PLA) or a copolymer of polylactic acid and glycolicacid (PLGA).
 2. The method as defined in claim 1, wherein theamphiphilic block copolymer containing a hydrophilic block (A) and ahydrophobic block (B) is an A-B, A-B-A or B-A-B type block copolymer. 3.The method as defined in claim 1, wherein the poorly water-soluble drugis paclitaxel, docetaxel, 7-epipaclitaxel, t-acetyl paclitaxel,10-desacetyl-paclitaxel, 10-desacetyl-7-epipaclitaxel,7-xylosylpaclitaxel, 10-desacetyl-7-glutarylpaclitaxel,7-N,N-dimethylglycylpaclitaxel, 7-L-alanylpaclitaxel, ternsirolimus or amixture thereof.
 4. The method as defined in claim 1, wherein thehydrophilic block (A) has a number average molecular weight of500-20,000 daltons, and the hydrophobic block (B) has a number averagemolecular weight of 500-20,000 daltons.
 5. The method as defined inclaim 1, wherein the ionizable salt is an inorganic salt.
 6. The methodas defined in claim 5, wherein the inorganic salt is one or moreselected from the group consisting of sodium chloride, sodium sulfate,magnesium chloride, phosphate salts, carbonate salts and bicarbonatesalts.
 7. The method as defined in claim 1, wherein the ionizable saltis an organic salt.
 8. The method as defined in claim 7, wherein theorganic salt is one or more selected from the group consisting oflactate, citrate, malate, succinate, tartarate, fumarate, ascorbate,glutamate, gluconate, sebacinate, malonate, salicylate, acetate andsorbate salts of alkaline metals.
 9. The method as defined in claim 8,wherein the organic salt is one or more selected from the groupconsisting of sodium lactate, sodium citrate, sodium malate, sodiumsuccinate, sodium tartarate, sodium fumarate, sodium ascorbate, sodiumglutamate, sodium gluconate, sodium sebacinate, sodium malonate, sodiumsalicylate, sodium acetate and potassium sorbate.
 10. The method asdefined in claim 1, wherein at least 95% of the poorly water-solubledrug is stable for 12 hours without precipitation when in areconstituted solution with distilled water for injection, 0.9%physiological saline or 5% aqueous dextrose solution.
 11. The method asdefined in claim 1, wherein the lyophilization aid is one or moreselected from the group consisting of lactose, mannitol, sorbitol andsucrose.
 12. The method as defined in claim 1, wherein the organicsolvent is one or more selected from the group consisting of acetone,ethanol, methanol, ethyl acetate, acetonitrile, methylene chloride,chloroform, acetic acid and dioxane.
 13. The method as defined in claim1, wherein the organic solvent is used in an amount of 0.5-30 wt % basedon the weight of the micelle composition.